trebor Posted November 7, 2019 Share Posted November 7, 2019 It's easy to get them one tooth out Link to comment Share on other sites More sharing options...
tigerman Posted November 7, 2019 Share Posted November 7, 2019 Thanks Jon ,that would be the reason why this Laser 80 was fine in my Wots Wot with a 14x7 prop and then I put in this model with a 15x 8 and it has given me problems .I have put a 14x7 prop back on the Laser 80 and had it is much better , It running a treat now ,Thanks Jon and everyone who help me Edited By tigerman on 07/11/2019 15:35:57 Link to comment Share on other sites More sharing options...
Edgeflyer Posted November 7, 2019 Share Posted November 7, 2019 Thanks Jon. I will see if my local outlet has bs008 o rings. I will try harder next time. My 150 has to be cleaned next. Link to comment Share on other sites More sharing options...
Paul james 8 Posted November 11, 2019 Share Posted November 11, 2019 Is this the correct forum to ask whether my Almost new Laser 200 v twin would be powerful enough to use on a Seagull FW190? The model has an 80" wingspan and is rated 33 to 35cc. All up weight suggested as around 15lbs. Any advice appreciated or if wrong forum where to alternatively post. Link to comment Share on other sites More sharing options...
Jeremy Scott-hake Posted November 14, 2019 Share Posted November 14, 2019 The Seagull FW 190 and the Laser 200 should be fine, I have the same combo but not finished or flown. Link to comment Share on other sites More sharing options...
Jon H Posted November 14, 2019 Author Share Posted November 14, 2019 Yep, it will be fine although 15lbs is a fantasy. In fact i just checked the seagull website and they are now saying 20lbs which is more in line with what i would expect. At 20lbs the 200 will be fine but if you can get it down to 18 you will be even better off. Use 18x8 2 blade props for max overall performance but you could also try 19x8. I suspect there is room to reduce the weight as the 190 has an extremely short nose and ballast will be needed. If you get all the batteries and radio well forward, and then make a tray in the cowl under the engine for ballast to sit on you can get the weight much further forward and reduce the amount of it you need. Looking at the instructions i would probably move the servos forward as they are behind the c/g, and i would mount the engine upright with the tanks in the top of the fuselage. If mounted inverted there is nowhere for the tanks to go as they would need to mount really low and there is stuff in the way. Link to comment Share on other sites More sharing options...
Paul james 8 Posted November 14, 2019 Share Posted November 14, 2019 Thanks Jon, Don't have the model yet, it has already been built. Am I going to need two tanks, one for each cylinder? If so what size would you recommend? Link to comment Share on other sites More sharing options...
Jon H Posted November 14, 2019 Author Share Posted November 14, 2019 you can either use 1 tank with 2 clunks or 2 tanks. Either will work, but i am a fan of 2 tanks myself. This is because you can take a pair of slec tanks and tape them together to form one block. You then connect them together at the top so that when one it full it overflows into the next and fills that. I use this setup on my sea fury and it works very nicely and it means there is no danger of forgetting to fill the 2nd tank Its also handy using two tanks as i have had situations in the past where one tank was contaminated with some dirt and this blocked the fuel flow causing one cylinder to drop out. As the other tank was not contaminated the remaining cylinder continued to run and was enough to keep the model flying and allow power for a normal landing. If i was using only one tank there is a chance both cylinders would have been starved of fuel and the engine would have stopped. Not helpful in a 20lb warbird! There is no right answer here, just do whatever is easiest. You do need 2 clunk lines though, a T piece wont work as the one cylinder will steal fuel from the other and the slow run tuning will go out the window. Link to comment Share on other sites More sharing options...
Paul james 8 Posted November 14, 2019 Share Posted November 14, 2019 Thanks again Jon, all handy info that will help with the setup. I'm basing my decision on whether or not to buy the airframe on the practicality of the laser 200, which I already have, being powerful enough for the job. Link to comment Share on other sites More sharing options...
Jon H Posted November 14, 2019 Author Share Posted November 14, 2019 At 20lbs the 200 will fly a 190 with ease but the model wont 'sparkle'. My La7 is 80 inch and about 19lbs and is powered by a prototype 310v engine. The thing is a total animal and is well over powered. It started life with a laser 180 and it flew just fine, but it didnt quite have that sparkle i was looking for so in went a 300v. Immediately the difference was obvious, if a little over the top. The 200v is more powerful than the 180 and if you can build the 190 down to 18lbs then its really not going to disappoint. What i would do is weigh it with the engine before you buy and see if 18lbs is possible. Link to comment Share on other sites More sharing options...
Don Fry Posted November 15, 2019 Share Posted November 15, 2019 A weighted custom made spinner is also an option to get the weight forward. Link to comment Share on other sites More sharing options...
John Stainforth Posted November 15, 2019 Share Posted November 15, 2019 Don, Is it really such a good idea to hang a weight on a crankshaft? I would be interested in Jon's opinion. Link to comment Share on other sites More sharing options...
Ron Gray Posted November 15, 2019 Share Posted November 15, 2019 As long as it's balanced I can't see why not. I've run a big brass 'prop nut' to get the balance right on my Hurricane with Laser 180 and GA30 and no problems. Mind you in the event of a nose in you may find that there could be more damage! Just going back to the weight / engines discussion. The Hurricane mentioned above weighed in at 20lbs and when powered by the 180 or GA30 had nice scale like performance but like Jon said in his post, it didn't sparkle, so no 'monster' aerobatics - but I was more than happy with the performance. Edited By Ron Gray on 15/11/2019 07:17:34 Link to comment Share on other sites More sharing options...
Chris Walby Posted November 15, 2019 Share Posted November 15, 2019 Best get Jon's opinion on a "heavy" prop nuts as my mosquito (70's) has them and within reason, well machined (balanced) and not too heavy were considered ok. My Hurricane also has a brass prop nut most likely same as Ron's and is not an issue. The 180 is in the Yak for winter as it did not need the big nut and boy at tick over does the 180 shakes the Yak airframe! Link to comment Share on other sites More sharing options...
Jon H Posted November 15, 2019 Author Share Posted November 15, 2019 As long as its balanced and not stupidly heavy then a lump on the end of the crank is ok. I wouldnt want to be hanging lbs of weight out there but a heavy duty spinner adaptor isnt going to do any damage. If you do add weight to the crank i would pay double attention to bearing noise. If you hear any replace them immediately. Dont do what everyone else seems to do and wait for the cages to break up as the added weight on the crank will cause even more damage if they go. Link to comment Share on other sites More sharing options...
Martin McIntosh Posted November 15, 2019 Share Posted November 15, 2019 I have a 50cc petrol Hurricane. The 5" spinner was filled with lead, probably about a kg and over about 10 years of flying I have not noticed any problems. Great care was taken to ensure that it was perfectly level when pouring in the molten lead. Link to comment Share on other sites More sharing options...
Jon H Posted November 15, 2019 Author Share Posted November 15, 2019 Posted by Martin McIntosh on 15/11/2019 10:31:58: I have a 50cc petrol Hurricane. The 5" spinner was filled with lead, probably about a kg and over about 10 years of flying I have not noticed any problems. Great care was taken to ensure that it was perfectly level when pouring in the molten lead. While successful in Martin's case i would not recommend this. A slight out of balance resonance or even vibration related resonance and you will bend the crank before tearing the engine out of the model. While i cant provide figures as its not something i have tested i dont think i would want to add more than about 4 of 5 oz to a crankshaft on top of the spinner/prop weight, especially if its ahead of the prop. A heavier spinner backplate is a much safer option. Link to comment Share on other sites More sharing options...
Paul james 8 Posted November 15, 2019 Share Posted November 15, 2019 Been reading these posts about putting extra weight on the crankshaft, I have to say that it is a pretty awful solution from an engineering viewpoint. However well it might be balanced it adds weight for the bearings to support. As for using a kilo of lead in the spinner that is just scary! I make up adapter nuts to fit different sorts of spinners on some engines but try to keep the weight to a bare minimum. Tin hat on.....retreating to underground bunker!!! Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 15, 2019 Share Posted November 15, 2019 Just thinking out loud - gyroscopic precession must be a significant factor - probably more so in a 3D model than a warbird flown in a scale manner though... Link to comment Share on other sites More sharing options...
J D 8 Posted November 15, 2019 Share Posted November 15, 2019 Hawker had the same CoG problem with the full size and bolted lead to the engine bearers. Link to comment Share on other sites More sharing options...
Jon H Posted November 15, 2019 Author Share Posted November 15, 2019 Posted by Martin Harris on 15/11/2019 13:04:28: Just thinking out loud - gyroscopic precession must be a significant factor - probably more so in a 3D model than a warbird flown in a scale manner though... My P39 suffers from it quite a bit as its got a very long nose and a 5 inch ali spinner waving about at the front gives me all sorts of interesting pitch-yaw and yaw-pitch coupling. JD8, and there is a long threaded rod in the tail of a spitfire for the installation of lead disks. I guess thats what happens when to stuff a late series merlin or a griffon on the front of something not really designed for it! Link to comment Share on other sites More sharing options...
J D 8 Posted November 15, 2019 Share Posted November 15, 2019 Centre of gravity problems were common with many designs. Short Sunderland must be an extreme example. When it was found the wing needed to be a lot further back it was decided rather than redesign the hull the wings were given sweepback at the root. They did not bother to realign the engines so they toed out. This lost some performance but was helpful in engine out situation. John. Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted November 15, 2019 Share Posted November 15, 2019 Apparently this wasn't in response to initial design failings but due to the Air Ministry requesting a powered 4 gun turret be installed in the tail during assessment of the prototype. Edited By Martin Harris on 15/11/2019 14:57:19 Link to comment Share on other sites More sharing options...
bert baker Posted November 15, 2019 Share Posted November 15, 2019 Posted by John Stainforth on 15/11/2019 06:54:49: Don, Is it really such a good idea to hang a weight on a crankshaft? I would be interested in Jon's opinion. The boat brigade, car and helicopter fans have done it for many years, Link to comment Share on other sites More sharing options...
John Stainforth Posted November 15, 2019 Share Posted November 15, 2019 Posted by bert baker on 15/11/2019 15:24:00: Posted by John Stainforth on 15/11/2019 06:54:49: Don, Is it really such a good idea to hang a weight on a crankshaft? I would be interested in Jon's opinion. The boat brigade, car and helicopter fans have done it for many years, Good point. Link to comment Share on other sites More sharing options...
Recommended Posts